The new method and packing arrangement is essentially meant for producing a packing arrangement, which compensates for the wear and volume changes of seal material and of the cylinder, in which the said seal is moving axially and/or radially against metal surfaces to be sealed.
Accordingly an object of this invention is to provide a simple method for producing a packing arrangement for purposes, in which an elastic seal material, preferably PTFE compound, is compressed to its final shape at room temperature by means of press members made of steel, the press members being movable against each other by force to compress said seal material placed therebetween, thus forming an elastic seal material layer for sealing a gap between surfaces to be sealed, and which the packing arrangement is capable of compensating the temperature changes and the wear of seal material.
Another object of the invention is to provide an adjustable packing arrangement, particularly for a hydraulic fluid operated or mechanically operated system, which the arrangement is capable of withstanding substantial high pressures, even pressures of several hundred bars in a wide temperature range, but being suitable for minor pressures as well.
Still another object of the present invention is to provide a packing arrangement that is displaceable in an axial direction inside a cylindrical/tubular space, said packing arrangement being also suitable for the axially surrounding sealing of a shaft which is rotatable and/or axially displaceable within said space.
Still another object of the invention is to provide a relatively simple and effective packing arrangement for packing or sealing cylindrical/tubular spaces or shafts operating in such spaces, especially when applying relatively high operating pressures.
A packing arrangement of the invention finds a plurality of applications in mechanical seal components having considerable pressure differences on both sides to be sealed, e.g., flap-valves, ball valves, pistons etc. This type of seal and packing arrangement also can be used in any geometrical form of pistons and cylinders, which are used for seal arrangements on various designs in a machine construction.
To achieve the above and other objects of the invention, there is provided a method for producing a packing arrangement for a hydraulically operated apparatus, said method being characterized by the following steps:
(a) producing a preshaped plastic piece of seal material; PA1 (b) compressing said preshaped piece at room temperature into a cylinder; and PA1 (c) compressing said preshaped piece at room temperature to its final form in said cylinder between a piston member and a counterpress member, at least one of said piston member and counterpress member being provided with rounded or tapered head portion facing against said preshaped piece, whereby the cross-section of said final compressed seal member is essentially wedge-shaped.
There is also provided a packing arrangement displaceable in an axial direction inside a cylinder/tubular space, characterized in that said packing arrangement includes: two metallic compression elements axially displaceable relative to each other, whose relative rotation is prevented, and a seal member, fitted between compression elements and cold-molded at room temperature from a blank and whose material comprises quite easily plastically moldable materials with a low friction coefficient, especially PTFE plastics in various compounds, or graphite, said cold-molding being effected by means of said compression elements in a cylinder/tubular space, said space serving as a final operating location for the packing arrangement or corresponding in its dimensions to a final operating location for the packing arrangement; that a molding surface included in at least one of the compression elements and positioned against seal member is designed to be conical or convex toward the seal member, whereby the seal member has a wedge-shaped cross-section after said molding, and that said packing arrangement further includes means for moving said compression elements axially toward each other for squeezing a seal member fitted therebetween against the wall of space to be sealed with an appropriate initial tightness prior to the application of the pressure effect of a pressure medium/instrument on said packing arrangement.
According to another aspect of the present invention there is also provided a packing arrangement for sealing or packing a shaft rotatable and/or axially displaceable in a cylinder/tubular space, characterized in that said packing arrangement includes: two metallic compression elements, axially displaceable relative to each other and surrounding a shaft to be sealed, whose relative rotation is prevented, and a seal member, fitted between compression elements, set against said shaft and cold-molded at room temperature from a blank, whose material comprises quite easily plastically moldable, low friction coefficient materials, especially PTFE plastics in various compounds or graphite, said molding being effected by means of said compression elements; that a molding surface included in at least one of the compression elements and abutting against the seal member is designed to be conical or convex toward the seal member, whereby said seal member has a wedge-shaped cross-section after said cold-molding; and that said packing arrangement further includes means for moving compression elements axially toward each other for pressing said seal member fitted therebetween against said shaft to be sealed with an appropriate initial tightness prior to the application of the pressure effect of a pressure medium/pressure instrument on the packing arrangement.
One advantage gained by a packing arrangement of the invention is its relatively simple installation as the packing arrangement can be set up with relatively wide tolerances.
Thus, the packing can be installed in position by allowing first some pressure medium therethrough for the easy removal of any possible air entrapped in the pressure medium prior to the initial tightening of the packing, during which the seal member is brought into a sealing contact against a surface to be sealed. Following the initial tightening and by virtue of the structure of a packing arrangement, the pressure effect applied to the packing arrangement by a pressure medium subjects the seal member to a pressure exceeding that of the pressure medium, whereby the seal member presses more tightly against a surface to be sealed for preventing leaks through the packing arrangement. The selection of a coning angle can be used to provide a desired pressure reinforcement in the seal member.